We have checked all the outlets and light switches and they all work. The power went out in three rooms and breaker did not trip. We took pictures of the breaker wires and noticed this one wire looked discolored. Do you think this maybe the reason the power is out? Does the wire look burned?

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    That one wire did get hot enough to start melting the insulation. That should not happen, and it's interesting that the wire with the problem also looks like it was clamped down on in more than one spot as if to fix a bad connection. Did you attempt to re-clamp that wire or was it like that already?
    – JPhi1618
    Jun 3 '19 at 14:49
  • That wire was like that already. Since the power went off we have keep the breaker off. When it is on it does give us a reading of voltage. That is why we keep it off. Before the power went out the lights were flickering. So I think there was to much going on. Do you know if each neutral wire belongs to each breaker switch?
    – chelly
    Jun 3 '19 at 14:59
  • Each single hot wire (black) should be paired with a single neutral wire. There are some incorrect wiring techniques that can lead to two hot wires sharing a neutral, and then the neutral can be dangerously overloaded. This can happen due to inexperience or even accidentally (mixed with inexperience).
    – JPhi1618
    Jun 3 '19 at 15:05
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    @jphil you are wrong , a code recognized method of running 2 hots on 1 neutral is totally code compliant and is called a mwbc multi wire branch circuit. Covered in NEC 210.4. A loose connection can cause serious overheating and burn the hot or neutral completely off without causing an overload.
    – Ed Beal
    Jun 3 '19 at 15:21
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    OP did you loosen that screw? Compared to the others, it's loose as a goose. That would explain heat from arcing. Jun 3 '19 at 16:23

To me it looks like the wire may have been loose in the past and retorqued notice the gouge in the wire a torque driver was not used to do that much damage to the wire. Since you are having flickering or lights / circuits out and you have checked the panel it is time to find the problem. If you have other outlets or lights on that circuit that are working the problem will be at the last working outlet or device or the first non working one.

The most common cause is a back stab connection being used, these are when 14 awg wire is used and just pushed in to make the connection ( not under a screw or clamp), the next place is broken wires at a connection or 1 wire pulling out of a wire nut. I listed them in the order I find them in over the years. The big problems with back stabs is they may look fine on the outside but with a failed connection there is usually some deformation of the plastic and or insulation but you may have to look close. When you find the problem if the insulation is intact cut the arc marked wire back to good copper, this is enough as only the loose connection area was heated not the entire wire.

There is a small chance the problem could be a bad breaker, or panel and an even smaller chance it is a very old MWBC that did not have handle ties and the 2 breakers got separated and put on the same leg. To see if it is a MWBC trace that white wire back to the cable coming into the box. If there is only a black you are done. If there is a black and red (the most common hot colors) trace the black and red back to their breakers. They should be next to each other and by today’s code have handle ties, or a single handle, many years ago they just had to be in adjacent slots. If this is true the panel wiring is correct. If the breakers are separated someone messed up and they need to be together a handle tie or double pole breaker is the safe way to go.

Go back and find the source of the problem it usually is the last working outlet or device or the first non working outlet or device. And it could be the white or hot wire at those locations.

  • The gouge in the wire looks deep enough to me that it may have occurred as a result of melting at an earlier time. It would take a ridiculous amount of torque to cut that far through the wire, right? (Not saying some folks aren't that careless, but that's really deep.)
    – isherwood
    Jun 3 '19 at 15:50
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    I have seen it many times even by journeymen, that’s why torque drivers are required now.
    – Ed Beal
    Jun 3 '19 at 15:51
  • So, you're suggesting the melted insulation on the wire in the panel was because of the previous, possibly loose connection?
    – JPhi1618
    Jun 3 '19 at 16:03
  • I have seen melted insulation and burned off wires mor often than a split mwbc but I have found those in years past, I would say in the last 15 years I have found bad breakers more often than the couple of split up single breakers and tandem powering a mwbc. For those that don’t know a tandem or double stuff breaker is one that has 2 breakers on the same pole, mwbc circuits must be on opposite poles.
    – Ed Beal
    Jun 3 '19 at 16:08
  • @EdBeal In a factory I recently found a MWBC with 3 hots sharing a neutral. No, it wasn't 208/wye. Based on panel markings they were on L1, L1 and L2 respectively, but upside they were evenly loaded and used at the same time, so that probably saved them. Jun 3 '19 at 16:28

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